1. Field of the Invention
This invention relates to a process for etching an aluminum layer. More particularly, this invention relates to a process for etching an aluminum layer, using one or more bromine-containing etch gases to form a pattern of aluminum during the fabrication of an integrated circuit structure on a semiconductor wafer without incurring the risk of corrosion problems normally encountered in etch processes using chlorine-containing etchants.
2. Description of the Related Art
Conventional plasma etching of an aluminum layer in the fabrication of integrated circuit structures on semiconductor wafers utilizes Cl.sub.2 or a chlorine-containing gas, either of which can leave chlorine-containing residues on the remaining aluminum. While such a chlorine based etchant system is effective in etching away unmasked aluminum to form, for example, an aluminum wiring harness for an integrated circuit structure, chlorine residues which remain after the etch can result in corrosion of the aluminum lines upon subsequent exposure to air/H.sub.2 O.
The corrosion reaction degrades aluminum line continuity, and with a supply of H.sub.2 O (air), the reaction feeds itself, as shown in the following representative reactions: EQU 2 AlCl.sub.3 +3 H.sub.2 O.fwdarw.6 HCl+Al.sub.2 O.sub.3 EQU 6 HCl+2 Al.fwdarw.2 AlCl.sub.3 +3 H.sub.2
Sometimes the chlorine residues are contained (trapped) in sidewall materials which are deliberately formed on the sidewall of the aluminum line during the etch to inhibit undercutting of the aluminum line beneath the photoresist mask during the etch.
Conventionally, such sidewall deposits, which usually comprise oxide/polymeric materials, as well as such chlorine residues, are removed along with removal of the resist mask. Other chlorine residues on the aluminum are removed by washing the entire structure. However, in some types of processing, it is not convenient to either remove the resist and sidewall deposits immediately, or to immediately wash the semiconductor wafer to remove the chlorine residues, e.g., while carrying out processing steps under vacuum. Also, the corrosion reaction may occur very quickly (on the order of seconds or minutes) precluding the possibility of removing the sidewall deposits and residues before corrosion occurs.
This continued presence of such chlorine residues on a semiconductor wafer and the corrosive reaction of such residues with the aluminum lines formed on the wafer during the etch step can result in subsequent disruption of the normal function of the integrated circuit structure, where loss of aluminum from the aluminum lines results in an inability of the remaining portions of the conductive aluminum lines to carry the required electrical current. The corrosion reaction may continue slowly in the finished, packaged part, leading eventually to premature failure, limiting the overall reliability.
It would, therefore, be advantageous to provide a process for the selective etching of a masked aluminum layer to form aluminum lines without using chlorine-based etchants which leave corrosive chlorine residues on and in the integrated circuit structure formed on the semiconductor wafer.